i3wm is a dynamic tiling window manager primarily designed for X11 (one of the windowing systems used by Linux and other Unix-like operating systems). It is known for its efficiency and minimalism, providing a lightweight and customizable environment for managing windows. i3wm arranges windows in a tiled layout by default, which means that windows do not overlap and automatically resize to fit the available screen space. Users can navigate and control windows primarily using keyboard shortcuts, although it also supports mouse interaction.